Methylobacterium terricola sp. nov., a gamma radiation-resistant bacterium isolated from gamma ray-irradiated soil

Abstract

A gamma radiation-resistant and pink-pigmented bacterial strain, designated as 17Sr1-39^T, was isolated from a gamma ray-irradiated soil sample collected in the Republic of Korea. Cells were Gram-stain-negative, strictly aerobic, flagellated, asporogenous, rod-shaped and methylotrophic. Results of 16S rRNA gene sequence analysis showed that strain 17Sr1-39^T was phylogenetically related to <i>Methylobacterium currus</i> PR1016A^T (97.3 %), <i>Methylobacterium aquaticum</i> DSM 16371^T (97.2 %), <i>Methylobacterium platani</i> PMB02^T (97.0 %), <i>Methylobacterium frigidaeris</i> IER25-16^T (96.6 %), <i>Methylobacterium terrae</i> 17Sr1-28^T (96.6 %) and <i>Methylobacterium organophilum</i> JCM 2833^T (93.4 %). The G+C content calculated based on the genome sequence was 70.4 mol%. The average nucleotide identity and <i>in silico</i> DNA-DNA hybridization values between strain 17Sr1-39^T and <i>M. currus</i>, <i>M. aquaticum</i>, <i>M. platani</i>, <i>M. frigidaeris</i>, <i>M. terrae</i> and <i>M. organophilum</i> were 77.3-89.9 and 22-38.2 %, respectively. The predominant fatty acids were summed feature 8 (C_{18 : 1}ω7<i>c</i> and/or C_{18 : 1}ω6<i>c</i>) and summed feature 3 (C_{16 : 1}ω7<i>c</i> and/or C_{16 : 1}ω6<i>c</i>). The predominant quinone was ubiquinone 10 and the major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. Based on the data from phenotypic tests and genotypic differences between strain 17Sr1-39^T and its close phylogenetic relatives, strain 17Sr1-39^T represented a new species belonging to the genus <i>Methylobacterium</i>, for which the name <i>Methylobacterium terricola</i> sp. nov. (=KACC 52905^T=NBRC 112874^T) is proposed.